GB591041A - Radio navigation system and method - Google Patents

Abstract

591,041. Radiolocation. STANDARD TELEPHONES & CABLES, Ltd. April 27, 1945, No. 10725. Convention date, May 1, 1944. [Class 40 (v)] In a system for obtaining on one of a plurality of craft, indications of its distance from a single repeater station which simultaneously serves to repeat signals from other of said craft, on a common radio frequency, means are provided for distinguishing the respective indications at each craft from indications originating from other craft. In the embodiment shown in Fig. 1, the equipment at one aircraft comprises a wobbled frequency generator 1 supplying a pulse generator 2 and transmitter 3, so that radio-frequency pulses of variable repetition rate are transmitted from antenna 4. These pulses are picked up by antenna 5 at the single repeater station common to the system, and are automatically retransmitted from antenna 8, for reception at the aircraft on directional antenna 9. After detection in receiver 10, the pulses are fed to the control grid 12 of an oscilloscope 13. Energy from the pulse generator 2 is fed to a time base generator 14, which supplies time base potentials to the deflection coils 15 of the oscilloscope. Pulses from 2 are also fed through blocking circuit 11 to block receiver 10 during transmission. Deflection coils 15 are arranged to rotate around the oscilloscope simultaneously with the directional antenna 9. Thus each pulse radiated from 4 and received at 9 after retransmission from 8 produces a spot 18 on the oscilloscope, the distance of which from the centre indicates the distance of the craft from the repeater station, and the position of which round the screen indicates the bearing of the repeater station. Although the pulse rate is variable, the return pulses all give a coincident indication on the oscilloscope, since each outgoing pulse triggers the corresponding time base. Other aircraft such as 22 also interrogate the repeater station, but as the pulses are randomly related to the pulses. from the other craft, the direct and repeated pulses received at 9 occur at random in the time base sweep and do not give repeated coincident indications on oscilloscope 13. The true indications are clearly distinguished by their greater brightness. Instead of using pulses with a variable repetition rate, the pulses from each aircraft may have different repetition rates.